A fluorescence in-situ hybridization (FISH) method will be further developed and utilized as a major procedure for the high resolution quantitation of the frequency of cycling AML cells. AML diseases associated with the following chromosomal abnormalities will be studied by this procedure - inv(16), t8;21, t15;17, +8, and -7. The procedure is based on our results in CML where we have coupled long term mitotic arrest to produce thousands of metaphases/slide ("hypermetaphase") with the use of a FISH probe that detects the chromosomal rearrangement associated with the malignancy (hypermetaphase/FISH or HMF). In the CML model we have demonstrated that cancer cells could be readily quantitated in cycling cells from patient bone marrow preparations. The procedures will allow detection of <1% cancer, calls and will permit monitoring of <4% changes in the frequency of such cells. The methodology will be applied here to identify severity of disease in AML patients at diagnosis and to evaluate the effectiveness of therapies on AML patients during treatment. The data from +8 and -7 will be correlated with the interphase FISH data on those same samples generated by Core C. In addition we will conduct reverse transcription followed by PCR (RT/PCR) to determine the level of chimeric transcript in t15;17 and t8;21 AMLs to correlate with the HMF data as well as the interphase FISH and standard G-band cytogenetics (CG) data generated on the same samples by Core Finally we will complete development and conduct genomic PCR on inv(16) samples to evaluate the level of cells containing the chimeric gene reactive to our HMF results as well as RT/PCR, interphase FISH and CG conducted on those same samples. The experiments and correlations will be evaluated with the progress of the patients determined by Projects 1 and 2 (Drs.Estey and Champlin respectively) to determine the benefits and shortcomings of each of the technologies in establishing the cytogenetic response of patients to therapies involved. These procedures will give us new insights into determining the clinically significant level of residual disease, and guide the further management of individual malignancies in AML patients.